Boston fast food workers walked off their jobs Thursday as part of a national strike calling for a $15 minimum wage.

Boston fast food workers walked off their jobs Thursday as part of a national strike calling for a $15 minimum wage.

Fast-food workers in hundreds of cities across the United States kicked off a day of strikes and rallies on Thursday to demand a higher living wage.

Workers want the federal minimum wage raised to $15 from $7.25, saying the current rate is not enough to live on. Critics counter that doubling the minimum wage would cost jobs, forcing employers to cut back on the number of workers.

More than 42,010 Bay State fast-food workers earn a median wage of $9.30 an hour, according to protest organizers, Mass Uniting.

Thursday's demonstrations come after protests held on Black Friday, the day after Thanksgiving, by Walmart workers at about 1,500 U.S. stores. There were also strikes by fast-food workers in dozens of cities in August.

Fast-food workers say that today's minimum wage is not adjusted to inflation, as Congress has done since the first minimum wage was set in 1938.

They say they are forced to rely on federal aid to support themselves and their families.

Data from the U.S. Census Bureau and public benefit programs show 52 percent of fast-food cooks, cashiers and other staff relied on at least one form of public assistance, such as Medicaid, food stamps or the Earned Income Tax Credit program, between 2007 and 2011, according to researchers at the University of California-Berkeley and the University of Illinois.

Some economists also argue that increasing the minimum wage could help stimulate the U.S. consumer economy because workers would have more money to spend.